This invention is in the field of solid materials handling, and relates to using recycled material (especially from discarded carpet segments) to create large sheets of wood-like material, comparable to sheets of plywood, that is highly resistant to infiltration or damage by water and various chemicals and solvents.
Various methods are known for converting recycled waste products containing nylon and other plastics into relatively narrow planks. Those recycled planks typically resemble single boards, rather than sheets of plywood, and typically have widths only up to about 15 cm (6 inches) wide. Most manufacturing processes used to create such board-substitutes from recycled wastes require a relatively high level of melting of the nylon or other plastic material in the recycled feedstock mixture. Accordingly, such manufacturing processes require large amounts of energy, to heat up the recycled materials to their melting points.
By contrast, prior to this invention, there has been no generally successful or widely accepted method of converting recycled nylon or other synthetic waste material into large board-like sheets with properties comparable to sheets of plywood (with regard to strength, durability, high but non-brittle levels of hardness and rigidity, etc.). A number of important and previously insurmountable obstacles apparently have prevented any such efforts from succeeding. Some of those obstacles can be summarized as follows.
First: it would require prodigious amounts of energy to heat the bulk and volume of material that would be involved in large-scale manufacturing of plywood substitutes, to the high temperatures that would be necessary in a manufacturing operation that requires extensive melting of recycled plastic or synthetic feedstock material.
Second: even if the necessary “average” temperatures could be reached, non-uniform heating would lead to unacceptable fault lines, fracture zones, weak spots, and other flaws, when large sheets of hard material are being manufactured. Those flaws would result in uneven strength, poor quality, and unreliability, if plywood-like sheets are being created, in ways that do not occur when narrow planks are created using melt-and-mold processes as used in the prior art.
Third: the problems of uneven heating (and resulting poor quality) are aggravated by the fact that when matted layers of fibers are heated, they respond in a manner directly comparable to thick woolen blankets. Fibrous mats are thermal insulators, and the type of thermal insulation they provide will thwart and frustrate any effort to establish the type of uniform and consistent heating that is required for a melt-and-mold manufacturing operation.
Fourth: serious problems arise when attempts are made to mix different types and grades of discarded nylon, and/or various other types of recycled plastics. As one example, in recycling operations used to create narrow planks of wood-like materials, care must be taken to avoid mixing a form of nylon called “nylon-6” with a slightly different form of nylon called “nylon-6,6”.
Fifth: still more serious problems arise, whenever attempts are made to force a liquified or paste (such as an adhesive, a melted component, etc.) to permeate, evenly and uniformly, through a dense layer of matted fibers.
For these and other reasons, all prior efforts to create large sheets of plywood-like material from discarded carpet segments (or other recycled textiles) apparently have failed. To the best of the Applicants' knowledge and belief, not a single product sold as a plywood substitute made from discarded carpet segments can be purchased, anywhere in the world. The closest comparable item that is available for sale is a synthetic waterproof sheet, made from highly expensive materials such as never-before-used spun fiberglass, held together with large quantities of expensive adhesives. Such sheets are sold as premium waterproof construction materials, by companies such as Coosa Composites LLC (Pelham, Ala.), at prices which average about $125.00 (wholesale price) for a single sheet which is ½ inch thick, and which is the same size as a standard sheet of plywood (8 feet long by 4 feet wide, or about 2.4 by 1.2 meters).
In addition to the absence of any commercially available products comparable to the products described below, the Applicant herein, a mechanical engineer who has worked for years in various fields relating to carpet recycling, has become aware of a number of failed efforts to create board-like materials, in sheets comparable to plywood, using discarded segments of carpet or other recycled synthetic fibers. None of those efforts ever succeeded, and the failed attempts typically were never published or patented. The most common problems encountered were excessive weight, excessive cost, and inadequate strength and/or durability (especially under wet conditions), for sheets of material that must compete against plywood in order to become commercially successful.
Despite decades of effort by hundreds of skilled people, carpet recycling still has not become fully viable on an economic basis. Every year, millions of tons of discarded carpet are sent to landfills. In his efforts to help the carpet recycling industry grow out of its struggling infancy, the Applicants herein kept their eyes open for various types of machinery that might be useful, somehow, in helping establish carpet recycling as a viable business, rather than a hopeful but marginal opportunity that is more neglected than used.
During the course of those efforts, the Applicants encountered an old type of machine that is usually called a “needle-punch” machine. These machines have been used for decades to rapidly punch flat layers of fibrous materials, for any of several purposes. Needle-punching is used to make various types of fabrics that have substantial thickness, such as blankets, quilts, draperies that can provide thermal insulation, etc. It is also used to make various industrial materials, such as filters that have substantial thickness, it is also used to create certain types of non-foam backing layers that provide insulation and padding when laid under a carpet. Needle-punching machines are sold by numerous companies, such as Foster Needles, Inc., Batson Yarn and Fabric, and various other companies listed in a directory that can be found on the Internet at www.davisongoldbook.com.
Because needle-punching operations are highly important in this invention, they are described in some detail below.
Needle-Punching Machines and Needles
During a needle-punching operation, a continuous sheet of matted fibers is carried forward, on a conveyor system, and is pulled through a needle-punching zone. In a typical machine, thousands of needles are held together in a spaced array by a large steel plate, referred to herein as a “platen”.
For convenience, all directions and dimensions referred to herein describe a matted layer of fibers that is carried horizontally on a conveyor system, while being needle-punched. In this arrangement, the platen which holds the needles is positioned above the layered material. The needles are vertical, with their sharp tips pointing downward. The platen (and all of the needles) are raised and lowered, in a reciprocating manner (typically, several times per second). During each downward stroke, the tips of the needles penetrate the fibrous mat. This is a conventional arrangement; if any other configuration is desired for a specific purpose, it can be provided in various ways, such as by using constraining guides, bulldozer-type gripping brackets, etc., to hold and support the material which is being needle-punched.
As the fibrous mat is slowly pulled through the needle-punching machine by the conveyor system, thousands of barbed needles are forced downward, through the mat, each time the platen is lowered. By the time the fibrous mat emerges from the needle-punching zone, the barbs on the needles will yank and pull tens of thousands of tiny fibers downward, in each square yard of the mat. In this manner, needle-punch machines are used to manufacture compressed fiber mats that have moderate cohesive strength without requiring glues, binders, or other costly chemical adhesives.
Needles that are used in this type of machine are usually referred to as “barbed” needles, or “felting” needles. These needles are sold by companies such as Foster Needles (Manitowoc, Wis., USA and Redditch, Worcester, England; Internet address www.fosterneedleusa.com).
The type of needle used in the operations discussed herein can be regarded as comprising five zones. As depicted in FIG. 2, which is prior art, the five zones of a needle 20 are referred to herein as the head 21, the platen zone 22, the neck 23, the barbed zone 24 with a plurality of barbs 25, and a non-barbed tip zone 26 (which includes a tip or point 27).
Barbed needles with various lengths are available. In needles that have been used to make the wood-like sheets described herein, the typical needle length is about 9 cm (about 3.5 inches). The tip zone 25 is roughly ½ cm long (about ¼ inch), has no barbs on its sides, and has a triangular cross-section. The barbed zone 24 immediately behind the smooth tip zone 26 is roughly 1 cm long (about ½ inch), and has a number of nicks or barbs (usually between 5 and 10) distributed around its periphery; in the needles used as described herein, it has a triangular cross-section. The neck 23, roughly 2 to 3 cm long (about 1 inch), is a smooth shaft with a round cross-section; it is relatively thin, to allow it to enter the fabric easily and with minimal yanking and stretching of the fibers it slides against.
The platen zone 22 is also round, but has a thicker diameter, for greater strength. It typically does not enter the fabric that is being punched. Instead, the platen zone 22 is designed to be securely held within a thick, heavy, metallic plate, called a platen, which holds thousands of needles in a regular geometric array (typically in a “diamond” pattern, with each row offset from the rows before and behind it).
The head 21 of needle 20 is bent at an angle (typically perpendicular) relative to the main shaft. This facilitates handling of these needles; such handling is necessary to remove worn or broken needles from a platen, and insert new needles into the holes that are vacated when worn or broken needles are removed. It also allows a locking plate to be placed on top of a platen, to lock the needles in place and make sure they cannot gradually become loose and slide upwards.
After seeing and studying a large needle-punch machine, the Applicants herein realized that this type of processing might be useful for processing a specific type of material he was closely familiar with. This material was created by a shredding device two of these inventors had previously invented and patented (U.S. Pat. No. 5,897,066, Bacon et al 1999). The entire contents of that '066 patent are incorporated by reference, as though fully set forth herein. FIG. 6 from that patent (which illustrates a “3-cylinder shredding machine”) is used as FIG. 3 of this application.
Briefly, the 3-cylinder shredding machine uses a claw drum for initial shredding, followed by passage of the shredded fibers between two drums that are run at different speeds. These two drums, rather than having claws or other cutting edges, have abrading surfaces, consisting essentially of rows of slightly elevated bumps and ridges. When used to shred segments of discarded carpet material, the combined actions of the claw cylinder followed by the two abrading cylinders being run at different speeds creates a relatively open and loose “fluff” material, comprising a mixture of nylon fibers from the tufting material of the carpet segments, and polypropylene fibers from the carpet backing layer.
In the manufacturing operation that was observed by the Applicants, that “fluff” material was being layered into mats by “garnett” machines (described below), to create low-density layers (also called “voluminous fiber”) roughly 1 foot thick. Those layers were then compressed and passed through a needle-punching operation, in ways that generated a moderately strong heavy layer of felt-like matted material, which was sold for use as an underlayment for carpets in high-traffic areas. Alternately, the matted material was cut and rolled into bales, which were sold and used as runoff-control barriers, to help reduce erosion in newly seeded areas alongside highways.
After seeing how that type of needle-punching operation was being used to create thick and heavy mats from discarded carpet segments, the Applicants began experimenting with segments of that type of needle-punched matted material.
The results eventually achieved have shown that discarded carpet segments can be processed to create inexpensive but very strong sheets of plywood-like construction materials, which have strength, durability, and handling traits (including the ability to withstand nails or screws near an edge, without splitting or fracturing) which are comparable to plywood, and in some respects substantially better than plywood. In addition, since this material is made from nylon and other hydrophobic synthetic fibers, it is much more resistant to infiltration or damage by water, than normal plywood.
Indeed, results to date indicate that its resistance to water is good enough to qualify as “waterproof”, as that term is defined and used by the construction and lumber industries. However, while more tests and scale-up work are being performed, the broader phrase “water resistant” is used to describe this product.
Accordingly, one object of this invention is to disclose a practical and economical method of using discarded carpet segments or other recycled textiles (preferably including only synthetic fibers) to make large sheets of wood-like materials that are comparable to plywood in terms of strength and weight, but which are more resistant than plywood to water infiltration and damage.
Another object of this invention is to disclose a practical and economical method of making a wood substitute, in sheets of any desired size, from discarded carpet segments.
Another object of this invention is to disclose methods of making water-resistant wood substitutes in sheets which are highly resistant to cracking, and which will not lose strength if a crack forms on one side, or near an edge.
Another object of this invention is to disclose methods of making water-resistant wood substitutes in sheets of any desired size, with a range of density, hardness, insulating, and other traits, by controlling various manufacturing parameters that determine the final thickness, density, and hardness of the resulting material.
Another object of this invention is to disclose methods of making water-resistant wood substitutes in sheets which can be as large as desired, such as a single waterproof sheet large enough to form the entire deck of a large boat, or an entire roof or floor of a large truck trailer or recreational vehicle.
Another object of this invention is to disclose methods of making building materials which can substitute for wood, thereby eliminating the need to cut down so many trees.
Another object of this invention is to disclose a commercially feasible and economic method of reducing and even entirely eliminating the solid waste problem created by millions of tons of carpet segments and other discarded synthetic fabrics that are currently being sent to landfills, every year.
These and other objects of the invention will become more apparent through the following summary, drawings, and description of the preferred embodiments.